This application claims the priority of application 197 14 118.8-21, filed Apr. 5, 1997 in Germany, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a bolt-on part, especially a front or rear bumper, of a motor vehicle that can be exposed especially in its outer area to impact energy and is mounted pointwise on a structural member on the vehicle, with the connection between the structural member and the bolt-on part comprising approximately pin-shaped mounting devices at one of the two parts to be connected and recesses on the other of the two parts, whereby in addition at least one of the recesses is enclosed circumferentially and is located at an end of the bolt-on part that is located furthest away from the point where the impact energy is applied in the direction of its action, while the other recesses are made open circumferentially.
Such a bolt-on part is known for example from Japanese Patent Document JP 071 37 585A.
In a bolt-on part of the type mentioned above, the invention is concerned with the problem, during an application of force caused by an impact, of avoiding deformation of the motor vehicle parts to which the bolt-on part is connected, up to an amount of impact energy that is as high as possible.
One solution to this problem is offered by a bolt-on part of the type mentioned above, wherein the circumferentially open recesses are in the form of grooves that are inclined by less than .alpha.=90.degree. to the direction of action of the impact energy.
The invention is based on the idea of permanently connecting the bolt-on part only at the end opposite the end that is exposed to a possible impact, to a structural member of the motor vehicle, while the remaining area is intended to be capable of shearing at the structural member on the motor vehicle. The shearing area is intended to deform in the shape of an arc and in the process to absorb as much of the deformation energy as possible to reduce the impact energy. The type of fastening that permits the shearing described above is provided by grooves that extend at an angle and are formed in the bolt-on part in such fashion that no hinge-like bending of the bolt-on part can take place in the groove areas during deformation caused by an impact. As a result of the inclined fastening of the mounting grooves, a certain amount of tolerance compensation in the lengthwise direction is possible when mounting on a part of the motor vehicle, if the mounting devices at the end of the bolt-on part are designed accordingly, with a recess that is enclosed all the way around. Such a design is achieved in the simplest fashion by a recess in the mounting devices that is in the shape of an elongate hole, for example.
As a result of the mounting grooves being at an angle, the bolt-on part is secured in a stable and nonbendable position with respect to the structural member to which it is connected, in a state in which it is not displaced lengthwise, in other words a state that is not influenced by an impact in the lengthwise direction.
The invention is especially advantageous in a U-shaped bolt-on part in which the recesses are located internally in the free legs and an impact is received in the direction of the legs, which is made on the closed U-area of the bolt-on part.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.